A blood test before the scalpel for canine splenic masses

CURRENT FULL VERSION: A blood-based answer to one of small animal practice’s hardest abdominal findings may be inching closer. New and emerging research on circulating microRNAs suggests clinicians may eventually have a preoperative tool to help distinguish canine splenic hemangiosarcoma from benign splenic disease, potentially changing how veterinarians counsel pet parents when a splenic mass appears on ultrasound. (journals.sagepub.com)

That need is well established. Splenic masses in dogs are common, especially in older patients, and their presentation can range from incidental imaging findings to collapse from hemoabdomen. ACVS says splenectomy remains both the primary treatment and the main route to diagnosis, because benign and malignant lesions can look similar clinically and on imaging. It also notes that up to two-thirds of dogs with splenic masses have malignant tumors, and two-thirds of those malignancies are hemangiosarcoma. (acvs.org)

The latest pathology study, published in Veterinary Pathology in 2026, evaluated 84 serum samples and 84 tissue samples spanning eight splenic mass categories plus controls from two institutions in Canada and Austria. Investigators reported that a 5-microRNA serum model, including miR-135a-5p, miR-10a, miR-450b, miR-152-3p, and miR-126-5p, correctly classified 24 of 24 dogs with hemangiosarcoma from healthy dogs and dogs with other splenic masses within the study cohort. The authors framed the work as a step toward a clinically useful screening or point-of-care test, while also emphasizing the need for future prospective and prediagnosis samples. (journals.sagepub.com)

This is not an isolated signal. Earlier work had already suggested that splenic hemangiosarcoma, nodular hyperplasia, and normal spleen have distinct microRNA expression profiles, with the stated long-term goal of a blood-based diagnostic test. Cornell researchers have also described preliminary serum findings in which miR-132 was increased and miR-486 decreased in dogs later diagnosed with hemangiosarcoma, and they are developing a rapid point-of-care platform intended to distinguish hemangiosarcoma from benign splenic disease. Separately, a 2026 AJVR report described a 4-microRNA circulating panel that discriminated dogs with splenic hemangiosarcoma from those with noncancerous splenic masses. (pmc.ncbi.nlm.nih.gov)

Industry and expert reaction is still emerging, but the direction of travel is clear: researchers are positioning microRNAs as a way to narrow a long-standing diagnostic gap. That gap matters because current tools are imperfect. Recent AVMA/JAVMA discussion of canine splenic cytology highlighted that agreement between cytology and histopathology is only moderate in practice. It also emphasized a point many clinicians already recognize: a neoplastic cytology result tends to be more predictive than a non-neoplastic one, so a benign aspirate should not be treated as a clean rule-out for cancer. The reasons are practical and biologic at once, including splenic heterogeneity, extramedullary hematopoiesis, mixed cell populations, overlap between reactive and neoplastic processes, and the basic sampling challenge of trying to characterize a large lesion with a small needle sample. In the same discussion, hemangiosarcoma and lymphoma were singled out as diagnoses clinicians most want to avoid missing, and serial ultrasound monitoring was described as a reasonable option in selected smaller, nonruptured nodules, while size and rupture risk may push the conversation toward surgery and definitive histopathology. (acvs.org)

The recent Veterinary Pathology paper explicitly argues that a concurrent diagnostic test could improve confidence in diagnosis and treatment planning, and Cornell’s project description says current decision-making often forces clinicians and pet parents to rely on statistics rather than individualized diagnostic information. In that context, a blood-based assay is attractive not because it replaces pathology, but because it could add another layer of preoperative evidence in the gray-zone cases where imaging and aspirates leave uncertainty. (journals.sagepub.com)

Why it matters: For practicing veterinarians, this research is less about replacing splenectomy tomorrow and more about improving the quality of decisions before the abdomen is opened. If a validated serum assay can reliably enrich suspicion for hemangiosarcoma, it could sharpen recommendations on referral, staging, perioperative planning, and expectations around adjuvant therapy. It may also help frame difficult conversations with pet parents facing emergency surgery, financial constraints, or uncertainty about prognosis. In incidental masses, the value could be even greater, because earlier risk stratification might support more deliberate planning before rupture or hemoabdomen occurs. It could also be useful exactly where current diagnostics struggle most: the “possibly neoplastic” aspirate, the benign-looking cytology that does not fully fit the clinical picture, or the patient being monitored with serial ultrasound where clinicians want a better sense of when observation is still reasonable and when surgery should move up the list. (journals.sagepub.com)

There are still important caveats. The strongest performance figures so far come from research cohorts, not broad prospective primary-care populations, and at least one study relied on samples collected at surgery or shortly before treatment rather than as a true screening test. The pathology authors themselves call for validation in additional populations and prospective samples, while Cornell’s program is still in pilot-development mode for a rapid assay. In other words, the science is promising, but it has not yet removed histopathology from the center of splenic mass diagnosis. (journals.sagepub.com)

What to watch: Watch for prospective clinical validation, commercialization or licensing activity around point-of-care assays, and evidence on how these tests perform in the messy middle, dogs with incidental masses, concurrent disease, anemia, hemoabdomen, or ambiguous imaging, and especially cases where cytology is equivocal or falsely reassuring, where a blood test would need to prove it changes care, not just classification. (journals.sagepub.com)